Multitude existing engines, such as aircraft engines, and also including automobile, marine, industrial and other engines, have multiple locations of relative motion. Relative motion exists everywhere adjacent hardware is linked with bearings or is bushed. When the engine is run continuously, even small displacements will wear at the linked or bushed interfaces. Current systems have high responses at the interfaces due to a match in natural frequencies and normal engine vibrations. Normal engine vibrations which are common to flight engines are those vibrations induced by rotating hardware
Additional vibrations are unique to particular systems. For example, vibrations may be caused from natural gas fuel. Natural gas is readily available and is the fuel of choice for most operators. This phenomenon is called combustor rumble. Combustor rumble imparts energy to the variable geometry system and is absorbed and damped at the linkage bearings and bushed interfaces.
Some engines, particularly continuously operated engines, can experience fleet-wide premature wear of high pressure compressor variable geometry hardware. The system wear is responsible for several undesirable conditions, such as unscheduled downtime to replace worn hardware; loose links from worn bearings; operational problems including reduced stall margin and degraded specific fuel consumption (SFC); and stage 2 high pressure compressor shroud and blade contact.
The current replacement rate of the high pressure compressor variable geometry hardware is between 8000 and 10000 hours, which is about equal to 15 months of field service. The expected durability of the variable geometry system is about 4-5 years. Several changes have been introduced in the art to improve component durability such as improved materials, anti-rotation features on bushings and lubricants in areas of relative motion between rubbing hardware and larger bearings in the links. However, these improvements are introduced as incremental improvements to make the hardware more tolerant of the engine system vibrations.
Specific components in the variable geometry system respond at resonant frequencies from normal engine vibrations. This results in extreme relative motion at the hardware connecting interfaces and has a significant impact on the service capability of the hardware.
It is seen then that it would be desirable to have a system and method which addresses the tendency of the hardware to deteriorate from resonating at their natural frequencies.